Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The stability of immobilized preparations of xanthine oxidase and urate oxidase was studied, and optimized, because of the potential joint use of both enzymes in clinical analysis. Xanthine oxidase was immobilized on cellulose, Sepharose, hornblende, Enzacryl-TIO, and porous glass. Thehalf-lives of these preparations at 30 degree C ranged from 40 min to 5.0 hr. In this respect immobilized enzyme resembled soluble enzyme in dilute solution (0.11 mg/ml), when the half-live was about 3.5 hr. More concentrated enzyme solution (1 mg/ml) had a half-life of 64 hr, and was, therefore, considerably more stable than the untreated immobilized xanthine oxidase preparations. Inclusion of albumen in storage and assay buffer increased the half-life of bound xanthine oxidase. So also did treatment with glutaraldehyde: in the case of xanthine oxidase bound to Enzarcyl-TIO such treatment increased the half-life at 30 degree C from 3 hr to about 100 hr. Immobilized xanthine dehydrogenase was more stable than immobilized xanthine oxidase: the dehydrogenase lost no activity during continuous assay for 5 hr at 30 degree C. The stability of immobilized urate oxidase depended on the quantity of enzyme used and on the time of stirring during immobilization: thus a preparation was made (by stirring urate oxidase (48 mg/g support) with Enzacryl-TIO for 24 hr) which lost no activity during 350 hr at 30 degree C.
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PMID:Studies on the stability of immobilized xanthine oxidase and urate oxidase. 9 90

1. Concave-downward double-reciprocal plots were obtained for rabbit erythrocyte purine nucleoside phosphorylase when the concentration of Pi was varied over a wide range at a fixed saturating concentration of either inosine or deoxyinosine. Similar behaviour was also displayed by the calf spleen enzyme. 2. The degree of curvature of double-reciprocal plots was greatly modified by the presence of SO42-, introduced into the assay mixture with the linking enzyme xanthine oxidase; competitive inhibition by SO42- was observed over a narrow range of high Pi concentrations. 3. Partial inactivation with 5,5'-dithiobis-(2-nitrobenzoic acid) resulted in a marked alteration in the kinetic properties of the enzyme when Pi was the variable substrate. 4. Initial-velocity data are expressed in the form of Hill plots, and the significance of such plots is discussed.
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PMID:Rabbit erythrocyte purine nucleoside phosphorylase. Initial-velocity studies. 11 94

1. A method is described for the histochemical demonstration of the purine catabolizing enzyme guanase, employing glutaraldehyde fixation and Nitro blue tetrazolium (NBT). Parallel biochemical studies confirm that enzyme activity is not significantly inhibited by exposure to glutaraldehyde. 2. By this procedure guanase activity has been visualized in neurons and glial elements of the human central nervous system (CNS). 3. Controls consisted of direct incubation of cryostat sections with a specific inhibitor of guanase (5-amino-4-imidazole carboxamide) and omission successively of the substrate guanine, of xanthine oxidase and of NBT. Enzyme activity was completely inhibited by the above procedures, and by boiling of tissues for 10 min prior to fixation. 4. Levels of enzyme activity in spinal cord and brain were assessed by a subjective scoring method, and showed close comparability with biochemical assay data in brainstem and cerebral hemispheres; whereas a low correlation for enzyme activity was observed in spinal cord and cerebellum. Differences between biochemical and histochemical assessments of CNS guanase activity are discussed.
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PMID:The histochemical demonstration of guanase: observations in the human central nervous system. 11 16

The relationship between allopurinol oxidizing enzyme and aldehyde oxidase was investaged in mice. The oxidation of both N-methylnicotinamide and allopurinol appears to be catalized by a single enzyme, aldehyde oxidase (aldehyde-oxygen oxidoreductase EC, 1.2.3.1.). This conclusion is based on the following evidence; The postnatal changes of allopurinol and N-methylnicotinamide oxidizing activities were similar during growth and the levels of both activities increased in a parallel fashion upon the attainment of sexual maturity. The rates of loss of the activities of both enzymes by heat denaturation as well as dexamethasone administration were similar. The inhibitors of allopurinol oxidizing enzyme also suppressed N-methylnicotinamide oxidation. Competition of N-methylnicotineamide and allopurinol for oxidation was demonstrated. The rate of increase of the activities in both enzymes was almost parallel during each step of the purification from mouse liver supernatant. It was ascertained that xanthine oxidase in the enzyme preparation does not influence allopurinol oxidation.
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PMID:[Hepatic allopurinol oxidizing enzyme in mice]. 12 99

A suspected case of xanthine oxidase deficiency has been further investigated. The patient complained of arthralgia and myalgia. Further studies included histochemical and ultramicroscopic analysis of muscle sarcoplasmic reticulum, and biochemical studies. High levels of xanthine and hypoxanthine were found, while uric acid was absent in the muscle extracts.
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PMID:Xanthine, hypoxanthine and muscle pain. Histochemical and biochemical observations. 12 57

1. Ethanol metabolism in slices or homogenates of transplantable hepatocellular carcinoma HC-252 (HC-252) was 50 to 60% of the rate found in host liver slices or homogenates when they were expressed per gram of tissue wet weight and 70 to 80% of the liver when the rates were expressed per milligram of tissue protein. At 10 mM ethanol, the activities of alcohol dehydrogenase in tumor and liver supernatants were comparable. 2. Tumor microsomes did not oxidize ethanol in the presence of a NADPH-generating system, indicating the absence of the microsomal ethanol-oxidizing system and catalase-mediated peroxidation of ethanol. The HC-252 microsomes were contaminated with catalase, and acetaldehyde production occurred in the presence of a H2O2-generating system (xanthine oxidase). The virtual absence of ethanol oxidation and drug metabolism (aminopyrine demethylase and aniline hydroxylase) in HC-252 microsomes may be due to the low activities of NADPH-cytochrome c reductase, NADPH oxidase, and NADPH-dependent oxygen uptake. 3. Microsomal oxidation of ethanol was present in Morris hepatoma 5123C, a well-differentiated tumor of intermediate growth rate, while activity was negligible in microsomes from Morris hepatoma 7288CTC, a less differentiated tumor. Microsomal NADPH oxidase was present in the well differentiated tumor 5123C but was lacking in the less differentiated tumor 7288CTC. Several microsomal, mitochondrial, and cytosolic properties of HC-252 are similar to those of Morris hepatoma 7288CTC but differ from those of the more differentiated 5123C tumor and normal liver. 4. The content of mitochondrial protein in HC-252 was only 25% that of liver, and oxygen consumption per gram of tumor was only 28% that of the liver. When corrected for the mitochondrial protein content, oxygen uptake in tumor HC-252 and liver homogenates was comparable. Isolated tumor and liver mitochondria displayed comparable State 4 and 3 rates of oxygen consumption with succinate and glutamate as substrates. The activities of the reconstituted malate-aspartate and alpha-glycerophosphate shuttles were only slightly lower in isolated HC-252 mitochondria compared to liver mitochondria, when shuttles were reconstituted with purified enzymes. 5. Antimycin inhibited alcohol metabolism,and pyruvate stimulated alcohol metabolism, much less in tumor slices than in liver slices, suggesting the presence of an augmented mitochondria-independent, cytosolic mechanism for oxidizing reducing equivalents in the tumor. These factors suggest that oxidation of NADH is the limiting factor in ethanol metabolism. Whereas, in the liver mitochondrial reoxidation is predominant, in HC-252, cytosolic reoxidation of NADH also plays a major role.
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PMID:Ethanol metabolism by a transplantable hepatocellular carcinoma. Role of microsomes and mitochondria. 13 37

A 25-year-old white man with gout and nephropathy and with a previous reaction to allopurinol was given a trial dose of oxypurinol. He developed malaise, a generalized erythematous reaction with edema, pruritus, and emesis; this was clinically identical to the reaction he experienced with allopurinol. When the patient's lymphocytes were exposed in vitro to oxypurinol and allopurinol, increased DNA synthesis was observed, suggesting an immunologic basis for the reaction. This patient indicates that clinical cross reactivity to allopurinol and oxypurinol does occur and may be of an immunologic basis. There is a need for additional xanthine oxidase inhibitors for such patients.
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PMID:Allergic reaction to allopurinol with cross-reactivity to oxypurinol. 13 55

Detergent solubilized bovine milk fat globule membrane material studied by crossed immunoelectrophoresis combined with histochemical techniques revealed four major protein complexes. All four were found to bind to concanavalin A and three were identified as sialoglycoproteins. Xanthine oxidase activity was associated with the non-sialoglycoprotein precipitate. Immunoabsorption with intact milk fat globules showed an internal location of the xanthine oxidase, whereas the three other main proteins plus Mg2+-ATPase and 5'-nucleotidase were disposed on the outer membrane surface. The major proteins from milk fat globule membrane and membrane material isolated from skim milk showed immunochemical identity.
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PMID:Crossed immunoelectrophoresis of bovine milk fat globule membrane protein solubilized with non-ionic detergent. 13 25

A molybdenum cofactor (Mo-co) from xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) can be isolated from the enzyme by a technique that has been used to isolate an iron-molybdenum cofactor (FeMo-co) from component I of nitrogenase. N-Methylformamide is used for the extraction of these molybdenum cofactors. Mo-co from xanthine oxidase activates nitrate reductase (NADPH:nitrate oxidoreductase, EC 1.6.6.2) in an extract from Neurospora crassa mutant strain Nit-1; however, FeMo-co is unable to activate nitrate reductase in strain Nit-1. Mo-co from xanthine oxidase is unable to activate nitrogenase in an extract of Azotobacter vinelandii mutant strain UW45. Inactive component I in this extract can be activated by FeMo-co. These results indicate that nitrate reductase and xanthine oxidase share a common molybdenum cofactor, but this cofactor is different from the molybdenum cofactor in nitrogenase.A. vinelandii synthesizes both Mo-co and FeMo-co. Mo-co is produced when the cells fix N(2) and also when they are repressed for nitrogenase synthesis by growth in a medium containing excess ammonium. However, FeMo-co is not produced when cells are grown in an ammonium-containing medium. Partially purified preparations of component I from A. vinelandii and Klebsiella pneumoniae contain both FeMo-co and Mo-co. The presence of both FeMo-co and Mo-co activities in partially purified preparations of component I explains previous reports of activation of inactive nitrate reductase in strain Nit-1 by acid-treated component I of nitrogenase. The Mo-co can be separated from FeMo-co in these preparations by chromatography on Sephadex G-100 in N-methylformamide. Both FeMo-co and Mo-co are sensitive to oxygen.
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PMID:Molybdenum cofactors from molybdoenzymes and in vitro reconstitution of nitrogenase and nitrate reductase. 14 98

Xanthine dehydrogenase (EC 1.2.1.37) is the first enzyme in the degradative pathway by which fungi convert purines to ammonia. In vivo, the activity is induced 6-fold by growth in uric acid. Hypoxanthine, xanthine, adenine, or guanine also induce enzyme activity but to a lesser degree. Immunoelectrophoresis using monospecific antibodies prepared against Neurospora crassa xanthine dehydrogenase shows that the induced increase in enzyme activity results from increased numbers of xanthine dehydrogenase molecules, presumably arising from de novo enzyme synthesis. Xanthine dehydrogenase has been purified to homogeneity by conventional methods followed by immunoabsorption to monospecific antibodies coupled to Sepharose 6B. Electrophoresis of purified xanthine dehydrogenase reveals a single protein band which also exhibits enzyme activity. The average specific activity of purified enzyme is 140 nmol of isoxanthopterine produced/min/mg. Xanthine dehydrogenase activity is substrate-inhibited by xanthine (0.14 mM), hypoxanthine (0.3 mM), and pterine (10 micron), is only slightly affected by metal binding agents such as KCN (6 mM), but is strongly inhibited by sulfhydryl reagents such as p-hydroxymercuribenzoate (2 micron). The molecular weight of xanthine dehydrogenase is 357,000 as calculated from a sedimentation coefficient of 11.8 S and a Stokes radius of 6.37 nm. Sodium dodecyl sulfate-gel electrophoresis of the enzyme reveals a single protein band having a molecular weight of 155,000. So the xanthine dehydrogenase protein appears to be a dimer. In contrast to xanthine dehydrogenases from animal sources which typically possess as prosthetic groups 2 FAD molecules, 2 molybdenum atoms, 8 atoms of iron, and 8 acid-labile sulfides, the Neurospora enzyme contains 2 FAD molecules, 1 molybdenum atom, 12 atoms of iron, and 14 eq of labile sulfide/molecule. The absorption spectrum of the enzyme shows maxima between 400 and 500 nm typical of a non-heme iron-containing flavoprotein.
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PMID:Regulation, purification, and properties of xanthine dehydrogenase in Neurospora crassa. 14 74


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